From 550cade20b272cef5d6c12c748d3629beba8c8c2 Mon Sep 17 00:00:00 2001
From: Alex Aizman <alex.aizman@gmail.com>
Date: Thu, 19 Sep 2024 09:26:49 -0400
Subject: [PATCH] new RMD _not_ to trigger rebalance when disabled in the
 config

* several distinct scenarios: by user, RMD with action message,
  RMD without message (ref)
* extra check in the latter case
* still trusting local copy of the cluster config, though

Signed-off-by: Alex Aizman <alex.aizman@gmail.com>
---
 ais/tgtcp.go     | 117 ++++++++++++++++++++++++++++++++---------------
 core/meta/rmd.go |   2 +-
 2 files changed, 82 insertions(+), 37 deletions(-)

diff --git a/ais/tgtcp.go b/ais/tgtcp.go
index 4e3df5d2d47..7671553f100 100644
--- a/ais/tgtcp.go
+++ b/ais/tgtcp.go
@@ -10,6 +10,7 @@ import (
 	"net/http"
 	"net/url"
 	"path/filepath"
+	"runtime"
 	"strconv"
 	"sync"
 	"time"
@@ -891,42 +892,7 @@ func (t *target) receiveRMD(newRMD *rebMD, msg *aisMsg) (err error) {
 		}
 	}
 	if !t.regstate.disabled.Load() {
-		//
-		// run rebalance
-		//
-		notif := &xact.NotifXact{
-			Base: nl.Base{When: core.UponTerm, Dsts: []string{equalIC}, F: t.notifyTerm},
-		}
-		if msg.Action == apc.ActRebalance {
-			nlog.Infof("%s: starting user-requested rebalance[%s]", t, msg.UUID)
-			go t.reb.RunRebalance(&smap.Smap, newRMD.Version, notif, t.statsT)
-			return
-		}
-
-		switch msg.Action {
-		case apc.ActStartMaintenance, apc.ActDecommissionNode, apc.ActShutdownNode, apc.ActRmNodeUnsafe:
-			var opts apc.ActValRmNode
-			if err := cos.MorphMarshal(msg.Value, &opts); err != nil {
-				debug.AssertNoErr(err) // unlikely
-			} else {
-				var s string
-				if opts.DaemonID == t.SID() {
-					s = " (to subsequently deactivate or remove _this_ target)"
-				}
-				nlog.Infof("%s: starting '%s' triggered rebalance[%s]%s: %+v",
-					t, msg.Action, xact.RebID2S(newRMD.Version), s, opts)
-			}
-		default:
-			nlog.Infoln(t.String() + ": starting rebalance[" + xact.RebID2S(newRMD.Version) + "]")
-		}
-		go t.reb.RunRebalance(&smap.Smap, newRMD.Version, notif, t.statsT)
-
-		if newRMD.Resilver != "" {
-			nlog.Infoln(t.String() + ": ... and resilver")
-			go t.runResilver(res.Args{UUID: newRMD.Resilver, SkipGlobMisplaced: true}, nil /*wg*/)
-		}
-		t.owner.rmd.put(newRMD)
-		// TODO: move and refactor
+		t._runRe(newRMD, msg, smap)
 	} else if msg.Action == apc.ActAdminJoinTarget && daemon.cli.target.standby && msg.Name == t.SID() {
 		nlog.Warningln(t.String()+": standby => join", msg.String())
 		if _, err = t.joinCluster(msg.Action); err == nil {
@@ -937,6 +903,85 @@ func (t *target) receiveRMD(newRMD *rebMD, msg *aisMsg) (err error) {
 	return
 }
 
+func (t *target) _runRe(newRMD *rebMD, msg *aisMsg, smap *smapX) {
+	const tag = "rebalance["
+	notif := &xact.NotifXact{
+		Base: nl.Base{When: core.UponTerm, Dsts: []string{equalIC}, F: t.notifyTerm},
+	}
+
+	// 1. by user
+	if msg.Action == apc.ActRebalance {
+		xname := tag + msg.UUID + "]"
+		nlog.Infoln(t.String(), "starting user-requested", t, xname)
+
+		// (##a)
+		go t.reb.RunRebalance(&smap.Smap, newRMD.Version, notif, t.statsT)
+		return
+	}
+
+	// 2. by RMD
+	xname := tag + xact.RebID2S(newRMD.Version) + "]"
+
+	switch msg.Action {
+	// 2.1. action => metasync(newRMD)
+	case apc.ActStartMaintenance, apc.ActDecommissionNode, apc.ActShutdownNode, apc.ActRmNodeUnsafe:
+		var opts apc.ActValRmNode
+		if err := cos.MorphMarshal(msg.Value, &opts); err != nil {
+			debug.AssertNoErr(err) // unlikely
+		} else {
+			var s string
+			if opts.DaemonID == t.SID() {
+				s = " (to subsequently deactivate or remove _this_ target)"
+			}
+			nlog.Infof("%s: starting '%s' triggered %s%s: %+v", t, msg.Action, xname, s, opts)
+		}
+		// (##b)
+		go t.reb.RunRebalance(&smap.Smap, newRMD.Version, notif, t.statsT)
+
+	// 2.2. "pure" metasync(newRMD) w/ no action - double-check with cluster config
+	default:
+		config := cmn.GCO.Get()
+		debug.Assert(config.Version > 0 && config.UUID == smap.UUID, config.String(), " vs ", smap.StringEx())
+
+		if config.Rebalance.Enabled {
+			nlog.Infoln(t.String(), "starting", xname)
+			// (##c)
+			go t.reb.RunRebalance(&smap.Smap, newRMD.Version, notif, t.statsT)
+		} else {
+			runtime.Gosched()
+
+			go func() {
+				smap := t.owner.smap.get()
+				if smap.GetNode(t.SID()) == nil {
+					nlog.Errorf(fmtSelfNotPresent, t, smap.StringEx())
+					return
+				}
+				config := cmn.GCO.Get()
+				if !config.Rebalance.Enabled {
+					//
+					// NOTE: trusting local copy of the config, _not_ checking with primary via reqHealth()
+					//
+					nlog.Warningln(t.String(), "not starting", xname, "- disabled in the", config.String())
+					return
+				}
+
+				// (##d)
+				nlog.Infoln(t.String(), "starting", xname)
+				t.reb.RunRebalance(&smap.Smap, newRMD.Version, notif, t.statsT)
+			}()
+		}
+	}
+
+	if newRMD.Resilver != "" {
+		nlog.Infoln(t.String(), "... and resilver")
+
+		// (##resilver)
+		go t.runResilver(res.Args{UUID: newRMD.Resilver, SkipGlobMisplaced: true}, nil /*wg*/)
+	}
+
+	t.owner.rmd.put(newRMD)
+}
+
 func (t *target) ensureLatestBMD(msg *aisMsg, r *http.Request) {
 	bmd, bmdVersion := t.owner.bmd.Get(), msg.BMDVersion
 	if bmd.Version < bmdVersion {
diff --git a/core/meta/rmd.go b/core/meta/rmd.go
index aedeec2614a..33151c69ead 100644
--- a/core/meta/rmd.go
+++ b/core/meta/rmd.go
@@ -5,7 +5,7 @@
 package meta
 
 type (
-	// RMD (Rebalance MetaData)
+	// Rebalance MetaData
 	RMD struct {
 		Ext       any      `json:"ext,omitempty"` // within meta-version extensions
 		CluID     string   `json:"cluster_id"`    // effectively, Smap.UUID